[martin-adams]

The latter probably runs the script as though you are within the context of a web page (so full Ajax/JS support).

I assume the Simple version might be completely written in Node.js - so parses the HTML content, but no dynamic scripting.

The important thing to note is that in the Dynamic, you can't use closures in your internal functions as it wont get executed within your Node.js context, but will in PhantomJS.

As for use case, I do it for https://myshopdata.com to allow retailers to extract their product information with rich content and variation support (even if loaded by the user interacting with a dropdown on variations). It then allows you publish this in marketplaces, while information in sync by monitoring.